Болсуновская Л.М., Абрамова Р.Н., Матвеенко И.А. (ред.) Petroleum engineering. Teachers book. Нефтегазовое дело. Книга для учителя
Подождите немного. Документ загружается.
41
2. For geophysical survey it is necessary to take measurements
systematically on land, at sea and in a borehole. When geophysicists
choose the particular methods for the survey they consider
homogeneity of the formation and contrasting properties of rocks.
3. The most use of such rock properties as elasticity, electrical
conductivity, density is made in geophysical survey. To a lesser extent
such property as radioactivity is utilized. Gravitational and magnetic
surveys use natural fields of force. Seismic and electrical methods
necessitate the introduction of some energy into the ground.
4. Many factors such as geological, economic and non-geological ones
determine the choice of particular type of survey. In many instances
geophysicists have to use different methods in combination. Gravity
and airborne magnetics can serve as a preliminary activity for seismic
shooting. Exploration for valuable ore deposits requires considering
results of electromagnetic, magnetic and gravity surveys.
5. We have to consider that geophysical survey costs a lot and does not
give very accurate results. In civil engineering where high accuracy is
required it is better to use exploratory drilling instead. In some cases
where area is large, depth is great and geology is simple, it would be
essential to do geophysical survey. In other instances when the cost of
drilling seems to be too high relative to the cost of geophysics but
penalties of inaccuracy are substantial it may be still cheaper to drill.
Exercise 22. Geophysics is a comprehensive, non-destructive, cost-effective,
efficient, and proven method of exploration. Explain each benefit of
geophysics with your own words.
“Benefits of Geophysics”. Environmental and Engineering Geophysics
offers a unique window into the earth as a means of detecting sub-surface
conditions, and its relevancy lies in the concrete and cost-effective
benefits it delivers. These include:
Comprehensive – Combinations of methods (i.e. multi-disciplinary
methods) provide the means of applying different techniques to solve
complex problems. The more physical properties that are evaluated, the
less ambiguous the interpretation becomes;
Non-destructive – It is ideal for use in populated areas, such as cities,
where many of today's environmental and engineering issues arise. It also
42
means an archeological site can be examined without destroying it in the
process;
Cost-effective – Geophysics does not require excavation or direct access
to subsurface (except in the case of borehole methods where access is
typically by drilled holes). This means vast volumes of earth can be
evaluated at far less cost than excavation or even grid-drilling methods;
Efficient – It provides a means of evaluating large areas of the subsurface
rapidly;
Proven – The majority of techniques have been in existence for more than
a half-century and are mature, yet still relatively undiscovered and
underutilized by decision-makers who face complex environmental and
engineering problems.
43
UNIT 2
GEOPHYSICAL METHODS IN PETROLEUM EXPLORATION
Lead-in. T. elicits the information from the Ss related to Oil Exploration.
This activity will prepare Ss to work with the topic of the Unit 2.
Look at the pictures and describe some operations or processes
associated with oil exploration.
(Pictures from the top and then to the right)
Drilling is directly connected with exploration operations as there exists so-
called exploratory drilling. Besides in seismic survey shot holes is a
necessary part of the whole process that is why seismic crew can include
from one up to four drillers.
Seismic survey is the most effective method for detecting hydrocarbon
reserves but it is very expensive and time consuming.
Elements of petroleum prospect must be present to initiate any type of
hydrocarbon exploration activities.
Electrical survey is one of geophysical methods of oil prospecting but its
application is limited as it cannot give enough information on the basis of
which it would be possible to conclude about the presence of hydrocarbon
deposits. It should be used in combination with other geophysical methods.
Name other activities, equipment that are necessary for oil exploration.
Activities:
регистрация данных – data acquisition
предварительная обработка – preliminary processing
интерпретация – interpretation
разбивка профилей – defining of seismic profiles
привязка сейсмических профилей на местности – seismic profile fixation
картирование площади – area mapping
фильтрация и усиление сигнала – filtration and signal amplification
Equipment:
gravimeters, magnetometers, seismogram equipment (сейсмозаписывающая
аппаратура), magnetic tapes, Vibroseis trucks, air gun arrays, seismometer
cable assembly (коса) and others.
Name occupations that are involved into petroleum exploration.
Seismic crew unites a group of people involved into different types of
exploration activities.
Seismic crew supervisor manages the acvitivity of a crew and reports to a
regional superintendent.
Geophysical engineer is in charge of quality and control of all survey costs.
44
Shooter blows up explosives at a predetermined time and cleans the well area
after the explosion.
Senior operator or observer is to monitor the accuracy of observation
schemes and quality of initial data.
Topographer is responsible for defining seismic profiles.
Calculator or seismic engineer in a local processing center prepares stacking
charts (схемы суммирования) and other materials for the conduct of the
subsequent interpretation.
Exercise 5. Form all possible nouns from the following words, use suffixes:
-ity, -or, -er, -ment, -ion, -sion, -tion, -ive.
Generate-generation/ generator, transmit-transmission/ transmitter, detect-
detection/ detector/ detective, attract-attraction, record-recorder, reflect-
reflection/ reflector, refract-refractor/ refraction, digitize-digitizer,
explore-explorer/ exploration, measure-measurement, dense-density, act-
action/ actor, susceptible-susceptibility, penetrate-penetration/ penetrator,
interpret-interpretation/ interpreter, explode-explosion/ explosive.
Exercise 6. Complete the sentences using correct prepositions where
necessary.
1. by 2. on, of, in, to, of, of 3. into 4. out, from 5. by 6. for 7. from 8. in 9.
on, in, on, at, on.
Exercise 7. Fill in the gaps.
1. seismic, magnetic, and gravity
2. magnetic
3. the air aeromagnetics or from a ship
4. reflection seismology and refraction seismology
5. analog signals
Exercise 8. Fill in the gaps with words which are derived from the word
given at the end of each line.
1. refraction
2. attraction
3. subsequent
4. predetermined
5. penetration
45
6. actuated
7. propagation
8. receivers
9. generation
10. explosives
Exercise 9. Give English equivalents to the following phrases.
1. Denser rocks have greater gravitational attraction than less dense rocks.
2. The exploration for valuable mineral deposits is carried out on land.
3. Sedimentary rocks have less magnetic susceptibility than igneous rocks.
4. Downward propagation of the sound wave made it possible to
determine location of the ship. 5. The air gun array generates seismic
waves which are reflected off the interface. 6. The modern technology of
collecting and processing data requires their digitizing. 7. Events can
penetrate deep into the Earth’s subsurface and subsequently yield
information about its interior. 8. The starting device embedded into
explosives was actuated at midnight. 9. The pull of gravity/ gravitational
attraction is determined by the mass of a body. 10. The thumping device
yielded energy of the required power.
Exercise 10. State whether the following sentences are true or false, correct
the false ones.
1. F – vice versa
2. F – magnetic method is the oldest one.
3. F – the gravity method is based on the measurements of the variations
in the pull of gravity from the rocks in the upper layers of the earth's
surface.
4. T
5. F – on land; At sea, a source such as an array of air guns is actuated
every few seconds as the ship moves over a predetermined course.
6. T
Exercise 11. Reconstruct the jumbled sentences.
1. The data are transmitted to a central recording unit.
2. Gravitational attraction is defined by the density of rocks.
3. In marine survey array of air guns is actuated.
4. The seismic waves are result of downward propagation of the source
energy.
46
5. Reflection seismology is based on measurements of the arrival times of
the events reflected from subsurface interfaces.
6. A central recording unit digitizes analog signals and records them for a
subsequent analysis.
7. A structural uplift of denser rocks will be shown as an anomaly on
gravity map.
8. Seismic energy may be generated by arrays of chemical explosions or
thumping device.
Exercise 13.
Listen to Khoi Pham who works for Geophysical Service
Incorporated. He tells about his position as a crew manager in marine
survey. Answer the questions given below.
1. He is in charge of all acquisition operations. His goal is to optimize
production and minimize the cost. He has to ensure safety and to
retreat streamers and maintain all the embedded gears.
2. Great. He started off as an observer and now he is a party manager.
3. An observer is in charge of all recording aspects of seismic, logging
data, keeping all the observations, monitoring the data quality.
4. An observer should have basic computer skills, organizational skills,
communications.
5. He can travel around the world, enjoy sea life.
6. He normally works twelve hours shift a day, seven days a week. Their
rotations range from six weeks on six weeks off plus-minus a week. It
depends but that’s a part of the job.
7. After shift he has full access to the Internet. There is gym facility, but
that’s honour. Lot of time he can just lie on the whole deck, go for
walks around the deck.
8. He was able to save a lot of money and buy two sports cars and do
enough smart applications to his cars.
Tapescript
My name is Knoi Pham. I work for GSI (Geophysical service
incorporated). Currently I’m on board of GSI Pacific. I’m a party manager
on board at the moment.
As a party chief I am in charge of all acquisition operation to the interest
of the client. My goal is to optimize production and minimize the cost. I
work together with the captain to ensure HSC procedures and how safety
47
is kept while on board. I tend to have to retreat streamers and deploy
streamers or responsible for maintaining all the embedded gears.
I started off as an observer. What observers do during acquisition, we’re
in charge of all recording aspects of seismic, logging, keeping any
observations that we see that are not normal, make sure the cable is
inspected or not, all the data is of quality. For an observer is important to
have basic computer skills, organizational skills, communications.
What makes this job interesting is that you get to travel around the world,
just being on the ship at sea, seeing sunrise, sunset, sea life.
We normally work twelve hour shift a day, seven days a week. Our
rotations range from six weeks on six weeks off plus-minus a week. It
depends but that’s a part of the job. On board after shift what we do for
spare time, we have full access to the Internet. There is gym facility, that’s
honour. Lot of time you can just lie on the whole deck, go for walks
around the deck. The off-time for six weeks is yours. You do whatever
you want. I often travel. I used all my time to travel.
Since working offshore with GSI I’ve been able to save a lot of money
and have bought a condominium. I mean I have two sports cars and do
enough smart applications to my cars, so I spend a lot of money there. I
have the luxury of buying all the gadgets and toys that I like. The money
scraped while you are offshore you can save and use it or put towards
anything you want.
48
Exercise 14. Tell about prospecting for oil using the following pictures.
Geophysical Prospecting: How to find oil!
1. In ancient times, oil was
collected at the surface.
2.
In the 19th century, holes were
drilled to depths of several
dozen meters.
3.
Today, drillholes reach as far
down as sev
eral thousand
meters.
From the time of high antiquity, in ancient Mesopotamia, oil that had
seeped to the surface was collected for medicinal use, as well as lighting
fuel and caulking for boats. Today, now that we have been producing
from accessible res
ervoirs for 150 years, it is increasingly hard to find
hydrocarbon-
impregnated rock. Explorers now have to look hundreds and
even thousands of meters below ground.
1. Map
2. Hammer
3. Acids
4. Magnifying glass
5. Logbook
The geologist's job is to observe, exp
lore and scrupulously record any
clue to the possible presence of hydrocarbons below ground. Geologists
are people of action and naturalists. They examine rocks and take samples
to ascertain their nature and date the strata from which they were taken.
They
then seek to reconstitute a scenario that may have been written 4
billion years ago.
49
1. Aerial shot.
2. Satellite shot.
Combined with aerial and satellite photographs, the geologist's
observations then serve to formulate initial hypotheses: yes, there
could
be oil down there, below ground, and it could be worthwhile looking
further.
Now it's the geophysicist's turn to study the physical properties of the
subsoil. A variety of methods are used at this stage, and a comparison of
their results serv
es to enrich the geologist's findings. Gravimetry measures
gravity, to give some idea of the nature and depth of strata depending on
their density. Magnetometry (generally performed from the air) measures
variations in the magnetic field. This gives an ide
a of the depth
distribution of crystalline terrains which have no chance of containing any
oil.
1. Signal emitted by vibrator
truck
2.
Reflected waves received by
geophones
3.
Data transmitted to laboratory
truck
A surface shock generates sound waves whic
h are refracted and reflected
underground. The way in which the waves are propagated varies as they
50
pass through the different strata. Using a highly-sensitive microphone
known as a "geophone," the geophysicist at the surface listens to the echo
of these waves and records them.
1. Isochrons
2. 3D seismic Maps
The geophysicist's seismic recordings are fed into powerful computers.
The terrain is mapped by means of isochronic lines linking points on the
ground at which the waves take exactly the same length
of time to be
reflected back to the surface. This method yields two and three
-
dimensional images of the underground strata, and the resulting seismic
maps serve to determine whether certain strata are likely to contain
hydrocarbons.
1. Seismic vessel
2. Hydrophones
In the oil man's jargon, exploration and production at sea is known as
"offshore." Because it is not practicable to survey the terrain at sea,
seismic methods are used systematically. And since ships can travel easily
in all directions, seismic measurement is in fact easier at sea than on land.
The geophysicist can thus obtain more data offshore than onshore and a
more precise three-
dimensional image, once the data have been processed.